Photoelectron spectroscopy of metastable AlF− negative ion

Abstract

We present the first experimental observation of the metastable AlF− negative ion. Velocity map imaging of the photoelectrons revealed that an electron is bound by 2.53 eV for AlF− with respect to the first excited state of the AlF neutral, a value much higher than the binding energies measured hitherto for metastable negative ions. Our calculations indicate this metastable state to be a 2Π state of AlF−. The flight times of ions in the present experiments indicate that these ions are long-lived with some ions surviving for such durations.